In many mining operations, the face is mined by a continuous mining machine having some form of cutting head on the front of the machine which mines the face and removes the minerals for transport to the surface. As the mining machine advances it is necessary to support the roof above the face, and this is commonly achieved by drilling long vertical holes upwardly into the roof and securing roof bolts in place using a quick setting epoxy cement. The holes for the roof bolts are sometimes drilled by a separate drill rig, and the bolts are then secured in place by an alternative power operated bolting socket.
In order to simplify the roof drilling and bolting operation it has become common place to mount the drill rig on the mining machine and to combine the drill rig and the power bolting socket in a single unit. This enables the roof bolts to be drilled and bolted from the mining machine as the machine advances into the face. Existing roof bolt drills of this type are however bulky and cumbersome to operate, frequently requiring the interchange of parts and/or the incorporation of a separate roof bolt drive socket after the drilling operation has been completed. The changeover between drilling mode and roof bolting mode takes time which of course slows the advance of the mining machine and restricts the rate of mining of the mineral face.
The bulky nature of the drilling and bolting mechanisms also limits the number of such drills that can be located side by side across the width of a mining machine and therefore restricts the pitch of the roof bolts which may be inserted using these conventional drills. Mining would be much safer if the bulk of the drilling and bolting machines could be reduced, allowing the machines to be located closer to the mining face, and furthermore allowing a greater number of machines to be placed side by side across the width of the continuous miner.
One of the reasons for the bulk of the machines is that the drilling operation requires a high speed drive with a relatively low torque requirement, whereas the bolting operation is not critical on speed but requires a high torque to securely fasten the nut on the roof bolt. To meet both of these requirements it has been necessary to provide a high speed, high torque drive motor which is large and bulky and which adds to the size of the roof bolt drilling machine.